1. Field of the Invention
This invention relates to automatically controlling the feed of lint cotton in a ginning process. More specifically, the lint cotton quality is measured and the feed of the lint cotton to the ginning process is adjusted accordingly.
2. Description of Prior Art
Automatically controlling the quality of cotton as it passes through the lint cleaning system without interrupting cotton flow through the ginning process has long been sought after by the growers, ginners, and spinners of cotton. Successful and efficient automatic control of cotton quality in the lint cleaning system can result in significant increases in high grade, longer fiber length, low nep count, and high bale weight cotton. Inevitably, this will translate into high bale value and low mill spinning cost.
Lint cleaning decreases trash content in the cotton and affects spinning performance. Increasing the amount of lint cleaning at the cotton gin reduces the amount of picker and card waste at the spinning mill. However, increased lint cleaning causes a greater number of neps in the card web, decreases yarn strength, and lowers yarn appearance, all of which reduce cotton value. Neps detract from the appearance of the material because they absorb dyes differently and appear as spots; low yarn strength, which is related to poor spinning and weaving performance, decreases the usefulness of a given cotton; and poor yarn appearance lowers the quality in many types of fabrics. (How Many Lint Cleaners Should You Use?, Mangialardi, Gino J., Jr., Cotton Ginners' Journal & Yearbook, March 1976.)
Increasing the number of lint cleaners also improves the grade classification which is a composite of the cotton's color and foreign-matter content, reduces fiber length, and increases the amount of waste material removed. Since bale value is based on the cotton's grade and staple length and the bale's weight, the addition of an extra lint cleaner will not necessarily give an increase in bale value but could give a bale value decrease. This would be the case when the weight removed and staple length reduction obtained by the use of the additional cleaner offsets the grade improvement. The number of lint cleaners required to give maximum bale value would be dependent upon the condition of the lint cotton before lint cleaning. In general, the early season harvested clean cottons would require less cleaning than the late season harvested more trashy cottons. (Multiple Lint-Cotton Cleaning: Its Effect on Bale Value, Fiber Quality, and Waste Composition, Mangialardi, Gino, J., Jr., Technical Bulletin No. 1456, August 1972.)
The grower is interested in producing the type of cotton that will yield the maximum bale value that will be consistent with satisfactory spinning performance. These two factors are controlled somewhat by prices and mill requirements. Based on prices when premiums for grade are small, attainment of maximum bale value depends on the ginner's ability to select the correct amount of lint cleaning. The number of cleanings should be applied to machine-harvested cotton to reduce its trash level only to the extent that will be consistent with highest returns.
Experiments have indicated that some cottons would require a degree of cleaning that would not be available with full stages of lint cleaning. For example, on a particular cotton maximum bale value might be obtained when using an amount of lint cleaning equivalent to a level between one and two stages.
Loading lint cleaners with cotton in the proper manner is one prerequisite to quality control during ginnery operation. This may be achieved by properly adjusting those factors related to loading. Two of these primary factors which affect batt conditions and could be controlled at the gin are lint feed rate and the cotton batt density.
Lint fed to the cleaning machinery at high rates results in decreased cleaning efficiency and produces lower bale values. Experiments show that decreasing these feed rates will give high significant increases in cleaning efficiency, higher grades, and some bale value increases, while causing no significant detrimental effect on fiber length, strength, or nep formation.
Lint batts fed to lint cleaners at high densities result in decreased cleaning efficiency and produce lowered bale values. Poor batt condition can also cause chokages and damage the equipment. (Effects of Feed Rate and Batt Density on Operation of Saw-Cylinder Lint Cleaners, Mangialardi, Gino J., Jr., Production Research Report No. 156, U.S. Dept. Agr., November 1974.)
Increase of mechanical action in cleaners by increasing the saw speed or combing ratio or both results in an increase in the cleaning efficiency and higher grades but also produces shorter staple length, an increase in the percent of short fibers, and an increase in the nep count level. Recommendations on saw speeds and combing ratios have to be a compromise between cleaning and fiber breakage. (Saw-Cylinder Lint Cleaning at Cotton Gins, Effects of Saw Speed and Combing Ration on Lint Quality, Mangialardi, Gino J., Jr., Technical Bulletin No. 1418, U.S. Dept. Agr., November 1970.)
It has been shown that as the moisture content of the lint increases the fibers become stronger and fewer fibers are broken by the lint cleaning actions. However, these moisture levels are also accompanied by decreased cleaning action. Thus, results show that the higher moisture cottons could and should be processed at higher saw speed or combining ratio or both for increased cleaning while the drier cotton, the fiber being more susceptible to damage, should receive the more gentle action at reduced saw speed and combining ratio. (Lint Cleaning at Cotton Gins: Effects of Fiber Moisture and Amount of Cleaning on Lint Quality, Mangialardi, Gino J., Jr., and Griffin, Anselm C., Jr., Technical Bulletin No. 1359, U.S. Dept. Agr., August 1966.)
Research experiments have shown that when premiums for grade are small maximum bale value can be best obtained by adjusting the degree of cleaning to produce cotton grade designation of Strict Low Middling White. It has been demonstrated that classer's grade should be given priority in controlling the degree of cleaning. Mass rate of flow of the cotton appears to be next in importance, followed by the moisture content, in controlling the amount of foreign matter extracted and thus the cotton's grade and bale weight.
Cottons processed at commercial cotton ginning plants are usually subjected to lint cleaning prior to baling. Lint cleaners used are principally of the controlled-batt saw type. In the average gin, cotton can be subjected to none, one, two, or three stages of lint cleaning. The ginner usually can select manually the number of lint cleaners to be used, based on his judgment as to the type and condition of cotton he believes he is processing. He has no control over saw speed, combing ratio, or lint batt density. These are set by the manufacturer at a constant speed and density. All cottons received at the gin plant normally receive the same lint cleaning treatment, although part of the lint-cleaning system is sometimes manually by-passed.